Automatic telephone system



T. G. MARTIN.

AUTOMATIC TELEPHONE SYSTEM.

APPLICATION FILED MAY 10. 1916.

Patented Apr. 5, 1921.

2 SHEETSSHEET 1.

I. G. MARTIN.

AUTOMATiC TELEPHONE SYSTEM.

APPLICATION FILED MAY 10, 1915.

13735624. Patented Apr. 5, 1921.

2 SHEETS-SHEET 2.

WV MQW UNITED 3T TEES Parent OFFPECE.

TALBOT Gr. MARTIN, OF CHICAGO, ILLINOIS, ASSIGNOR TO AUTOMATIC ELECTRICCOMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM.

Specification of Letters Patent. Patented Apr. 5, 1921,

Application filed May 10, 1916. Serial No. 96,495.

To all whom it may concern Be it known that. I, TALBOT G. MARTIN, acitizen of the United States of America, and a resident of Chicago, Cookcounty, Illinois, have invented certain new and useful Improvements inAutomatic Telephone Systerns, of which the following is a specification.

This invention relates to improvements in automatic telephone systemsand more particularly to improvements in theautomatic switches used insuch systems.

In many automatic telephone systems where ringing current isautomatically applied to signal the called line when connection isestablished therewith, an interrupt 111g device is employed to controlthe application of ringing current at certain intervals. Usually thisinterrupting device is common-to a group of lines or common to all thelines in the exchange, depending on the size of the exchange and theparticular arrangement desired. It a connection is completed to a calledline just after the ringing interval, the called line will not besignaled until the interrupting device reaches its next ringinginterval. The pe riod between ringing intervals is of some duration andit is therefore readily seen that some loss of time must be experiencedbefore the substation signal of the called' line is operated.

It is an ObJGCiJ oi this 1nvent1on to provide means whereby ringingcurrent for signaling purposes is projected to the called line theinstant connection is completed therewith.

A further object of this invention is the provision of an arrangement ofthis char acter whereby afterthe initial signaling operation, theinterrupting device controls the further ringing operation in theregular manner. 1 7

It is frequently impossible to limit the length of telephone linesleading from the subscribers stations to the exchange, especially isthis true in outlying exchanges wherelines extending from farmsubstations are served. Even in city exchanges some lines are of greaterlength and therefore greater resistance than others. In these instancesprovisions must be made for the eflicient control oi": certain relays inthe exchange by the longer lines which are necessarily of higherresistance than the shorter lines. In the switching mechanism hereindisclosed ringing current for signallng purposes is supplied through arelay which is so constructed and adjusted that it will not operativelyenergize during the signaling operations. In order that the said relaymay. properly operate to cut oil the ringing when in circuit with a lineof high resistance, I provide means comprising a booster battery'of suchvoltage as will permit suflicient flow of current to insure positiveoperation.

To the foregoing and other useful ends my invention consists of mattershereinafter set forth in the description of the drawings and in theappended claims.

The features of this invention will be more clearly understood byreference to the accompanying drawings in which Figures 1 and 2 takentogether represent a complete connection in an automatic telephonesystem embodying the principles of this invention.

The substation A (Fig, 1) comprises the usual receiver 3, transmitter4E, ringer 5, condenser 6, switch hook 7. It is also provided with asuitable impulse-sending mechanism or calling device for controllingautomatic switches, which mechanism is represented by a pair of impulsesprings 8 and an impulse wheel 9, which latter may be controlled by afinger hold dial (not shown) in such a way that the impulse springs aremomentarily separated a number of times corresponding to the respectivedigits of the called number. This impulse-sending mechanism may 'besimilar to that shown in United States Letters Patent to J. G. Blessing,No. 1,119,394, granted December 1-, 1914;.

T he subscribers individual or line switch (I is of the general type ofline switch disclosed in British patent to T. G. Martin No. 1419 or1910, being however, of the particular type disclosed, in United StatesLetters Patent to F. Newforth, Jr., No. 13,901, reissued April 13, 1915.The line switch comprises among other details the magnet 10 and slowacting line relay 11. Themagnet 10 controls the cutoff arm 12 andplungerarm 13 through the medium of the pull-in winding 14 and cut-onwinding 15. The winding 14: is strong enough to attract both the cut-offarm 12 and the plunger-arm 13 while the winding 1.5 is only strongenough to attract the cut-off arm 12 but will hold the plunger-arm 18 inits attracted position after it has been operated by the winding .14.The plunger-arm 13 carries on its end a plunger (not shown) which whenoperated forces the master switch D.

The master switch D is o1 the general type disclosed in British patentto lit. W. James No. 26,301 of 1906, being however, of the particulartype disclosed in the previously mentioned British patent to T.li/lartin. As herein represented the master switch comprises thestarting relay 2 locking magnet 25, motor magnet 26, and master switchwiper 27. The function of the master switch, as is well known, is tomaintain the plungers of all idle line switches in position to engagethe terminals of an idle trunk line.

The selector switch E is of the general type-oi": selector switchdisclosed in United States Letters Patent No. 815,321, granted March 13,1906, to Keith, Erickson and Erickson, except that the'side switch isdis pensed with and the circuits are modified to adapt the switch to oerate in a system in which the central otlice apparatus is 0011- trolledby impulses delivered over the two sides of the line in series. Thisselector being of the particular type disclosed in British Patent No.254:3 of 1914 to Automatic Telephone Manufacturing (10., Ltd. Amongother-details the selector comprises a bank of contacts arranged inhorizontal rows or levels, which are adapted to be engaged by a set ofwipers 28, 29, and 30, carried upon a shaft (not shown) which has avertical and rotary movement controlled by the vertical and rotarymagnets 31 and 32. The different operations of the sw1tch are controlledthrough the medium of the double- I wound line relay 3?). The releaserelay 84: and control relay 35 are slow-acting v1. 6., slow to releasetheir. armatures when their energizing circuits are broken. The relay 86controls the circuit of switching relay 37. The function of the latterbeing to eX- tend the connection through to the switch wipers.Therelease magnet 38 restores the switch shaft and wipers to normalposition whereupon oil-normal springs 39 and 4.0 are separated. The saidsprings 39 and 40 are closed when the shaft takes one or more steps fromits normal position.

The connector switch H 2) is of the general type of connector switchdisclosed inUnited States Letters Patent No. 815,17 6

granted March 18, 1906, to Keith, Erickson V shown in British patent toT. G. Martin J No. 1 119 of 1910, and further modified to operate inaccordance with the principles of my invention. Among other details theconnector comprises a bank of contacts ranged in horizontal rows orlevels which are adapted to be engaged by the wipers ll, 42, and 13carried upon a shalt (not shown) which has a vertical and rotarymovement controlled by the vertical and rotary magnets let and 45. Thevarious operations of the switch are controlled through the medium ofthe line relay 46. The release relay 17, private control relay 18 andcontrol relay 49 are slow acting, 2'. 6., slow to release theirarmatures when their energizing circuits are broken. The double woundrelay 50 is made slow acting so that will not opcratively energize byringing current when in the circuit of a condenser. The wiper cut-onrelay 51 energizes when the side switch reaches its third positioncontacts. The privatemagnet 52 controls the advance of the wipers 53 and5a in the well known manner. The busy relay 55 comprises two windings,the upper winding when energized attracts and operates its armature,while the lower winding will not operate the armature and is only usedfor resistance purposes as will be hereinafter esplained. The backbridge relay 56 supplies the called line with current for talkingpurposes. When energized the said relay 56 reverses the direction ofcurrent flow on the calling line which has no par ticular function inthe present disclosure but may beused for any desired purpose. Therelease magnet 57 is the medium through which the switch is restored toits normal position. When the switch shaft reaches its normal positionthe off-normal springs 58 and 59 are separated.

These springs are closed when the shaft takes one or more steps from itsnormal position.

The group relay 60 is energized intermittently through the medium of theconstantly rotating interrupter 61. When on crgized, said relay 60supplies ringing current over a common circuit controlled by the springs12a and 125 to a group of connectors, such as H, from the ringingcurrent generator B. When deenergized said relay 60 disconnects thegenerator R and substitutes the booster battery B.

The battery B having its positive pole grounded is used to supplycurrent for operating the automatic switches and for talking purposesaThe battery B has its nega tive pole grounded and is connected in aseries circuit with battery 13 when" relay 60 is deenergizedduring thesignaling operation.

The busy signaling machine 1 comprising the transformer windings 62 and63 and interrupter 64, is for the purpose of supplying a busy tone tothe calling line when a connection is attempted witha busy line,

The line switch F is similar in all respects to the line switch C andcomprises the cut-off winding 65, pull-in winding 66 and line relay 67.The substation J is similar in all respectsto the substation A.

A general description of the apparatus herein disclosed having beengiven it will now be explained how a connection can be establishedbetween the line of calling substation A and the line of calledsubstation J. Since the apparatus herein disclosed is in general wellknown in the art and is described in the publications herein referredto, its operation will be explained in a more or less general manner.

When the subscriber at substation A removes his receiver preparatory tomaking a call, an energizing circuit 1s closed for the line relay 11 ofthe switch C. This circuit extends from ground G through springs 68,line conductor 69, transmitter 4, receiver 3, impulse springs 8, switchhook springs 70, return line conductor 71, springs 72, line relay 11, tothe battery B. The line relay 11, upon energizing, closes the circuitfor the pull-in winding 14 extendingirom ground G through springs 73,the said winding 1 1, and master switch controlling contact 74 to thebattery 13. The winding 14: operates to thrust the plunger (not shown)on the end of the plunger-arm 13 into the bank of contacts 16-23 therebyforcing springs 16, 17, 18 and 19 into engagement with springs 20, 21,22 and 23, respectively, thereby extending the connection to theselector switch E. The cut-oil arm 12 is operated to remove the linerelay 11 from across the line. The relay 11 being slow acting, maintainsthe circuit of winding 14 for a short time after its own circuit isbroken. When the connec tion is thus extended an energizing circuit isestablished for the line relay of the selector E. This circuit extendsfrom ground G through the lower winding of said relay 33, springs 75,bank springs 23 and 19 over the circuit previously traced throughsubstation A back over bank springs 16 and 20, springs 7 6 and the upperwinding of said line relay 33 to the battery 13. Upon energizing, thesaid relay 33 closes a circuit from ground G through springs 77 and 78and release relay Bi to the battery B. The relay 3 1, upon energizing,closes a circuit from ground G through springs 7 9, conductor 80,springs 21 and 17 to a point 81 where the cir'cuit'divides, one pathextending through the holding winding 15 to the battery B, the otherpath extending over private normal conductor 82 to private bank contact83 and multiples thereof. This ground potential protects the substationA against seizure as long as the receiver is removed from theswitchhook. Due to the slow action of line relay 11 the circuit ofwinding 14 is maintained closed until after the holding ground from G issupplied over the conductor 30 to the winding 15 to maintain the plungerin its operated position.

Assuming the number of substation J to be 220, the calling subscribernow operates his calling device for the first digit 2, thereby causingthe impulse springs 8 to be momentarily separated twice, each timebreaking the circuit of the line relay 33. The slow acting relay 3% doesnot deenergize during the momentary interruptions of its circuit by therelay 33 and therefore each time the latter relay deenergizes an impulseis transmitted from ground G springs 77 and 8 1, springs 85, springs 36and 87, relay 35, and the vertical magnet 31 to the battery 13. Thevertical magnet receives two impulses over this circuit and operates toadvance the switch shaft and wipers two steps to a position opposite thesecond level of bank contacts, at the same time the pairs of springs 39and 10 are closed. The slow acting relay 35 ener izes when the firstimpulse of current is transmitted through it and holds its .armatureattracted during the subsequent impulses of the digit. in its energizedposition said relay 35 closes a circuitfrom ground G through springs 83and 39, and the relay 36 to the battery B. The relay 36, uponenergizing, forms a locking circuit for itself from ground G springs 79,con ductor 80, springs 90, springs 40, springs 91 and 92, and thesaidrelay 36, to the battery B. l/Vhen therefore, the relay 35 deenergizes after the last impulse is delivered through it to the verticalmagnet, the re lay 36 remains energized, and the circuit of the rotarymagnet 32 is closed over a circuit that extends from ground G to springs91 and 92 as previously traced, thence through springs 89 and 93,springs 9 1, and the rotary magnet 32 to the battery 13. The magnet 32,upon energizing, rotates the wipers 28, 29 and 30 one step and byopening the springs 90 and 9 1-, disconnects ground G from itseli andfrom the relay 36. 1f the first trunlrline of the second levelis idlethe relay 33de'e'nergizes as soon as the springs 90 are opened. If thistrunk line is busy however, the private wiper 29 finds the contact withwhich it engages provided with a guarding ground potential, which istransmitted to said relay 36 through its springs 91and 92 and tierebyprevents it from deenergizing. The rotary magnet 32 deenergizes whensprings 94 are separated regardless of whether or not the relay 36remains energized. 11" the relay 36 remains energized the circuit of therotary magnet will again be closed as soon as its armature falls backfar enough to close springs 90 and 94. The rotary magnet will thereforeenergize again and rotate the wipers onto the second set of bankcontacts which form the terminals of a second trunk line. If this secondset is also busy the rotary magnet will be again energized in the abovemanner to continue the rotation until the private wiper 29 encountersthe non-grounded contact of an idle trunk line, whereupon relay 36deenergizes. The relay 36, upon deenergizing, breaks the rotary magnetcircuit so that further rotation is impossible and closes the circuit ofswitching relay 37 which extend from ground G through springs 79,conductor 80, springs 90, springs 40, springs 91 and 95 and theswitching relay 37 to the battery B. The relay 37, upon energizing,disconnects the'line relay 33 from the line and extends the lineconnection over the heavy conductors through the wipers 28 and 30 to theconnector H. The line relay 46 of said connector thereupon becomesenergized and closes the circuit of release relay 47 from ground G7through springs 96 and 97 and the said relay 47 to the battery B. Therelay 47, upon energizing, completes a circuit from ground G throughsprings 98 and 99, release conductor 100, wiper 29, conductor 101 to apoint 102, where the circuit divides, one path extending through springs91 and 95 and the switching relay 37 to the battery B, the other pathextending through springs 40, springs 90, springs 21 and 17 and thecut-off winding 15 to the battery B. A branch of the circuit taps off atpoint 81 and extends over conductor 82 to private contact 83 and itsmultiples. The above traced circuit maintains the relay 37 and holdingwinding 15 energized after the relay 34 deenergizes shortly after theline relay 33 is removed from the line.

The calling subscriber now operates the calling device for the seconddigit 2, whereupon the impulse, springs 8 are separated twicemomentarily, each time breaking the circuit of line relay 46. y Therelay 47 being slow acting does not deenergize during the momentaryinterruptions of its circuit by the relay 46, and therefore each timethe latter relay deenergizes an impulse is transmitted over a circuitfrom ground G through springs 96and 103, springs 104, springs 105 and1.06 of relay 51, relay 48, vertical magnet 44, and the side switchwiper 53 (in first position) to the battery B. The vertical magnetreceives two impulses over this circuit and operates to advance theswitch shaft carrying wipers 41,42 and 43 two steps to a positionopposite the second row or level of bank contacts, at the same timesprings 58 and 59 are closed. A circuit is then closed from ground Gthrough springs 59, relay 49, springs 109 and 110 of relay 51 and thelower winding of relay 55 to the battery B. As before stated currentflowing in the lower winding of55 will not attract its armature. Relay49 energizes over this circuit and closes the contact of its springs 111and 112. The relay 48 is energized by the first impulse which istransmitted through it to the vertical magnet and retains its armatureattracted during the subsequent impulses of i the digit. In itsenergized position said relay 48 closes a circuit from ground G throughsprings 107 and 108 and the private magnet 52 to the battery B. Thiscircuit is broken when the relay 48 deenergizes a short time after thelast impulse has been delivered to the vertical magnet. The breaking ofthe circuit causes the privatemagnet to deenergize thuspermitting theside switch to pass from first to second position. In passing to secondposition the side switch wiper 53 transfers the battery connection tothe rotary magnet 45. It should be noted that. one pole of the generatorR is at this time connected through springs 112 and 111 (relay 49 beingenergized) springs 113 and 114 to spring 115 (relay 51 being as yetdeenergized).

The callingfsubscriber now operates the calling device for the lastdigit 0, in response to which the connector line relay 46 operates totransmit ten impulses to the rotary magnet 45, whereby the shaft wipersare rotated onto the contacts of the de- 105 and 106 of relay 51, relay48, springs 116 of relay 55, rotary magnet 45, side switch wiper 53 (insecond position) to the battery B; The relay 48 operates in response tothis digit in the same manner as for the previous digit to advance theside switch another step, 2'. a, from second to third position. Upon theengagement of the side switch wipers 53 and 54 with their third positioncontacts, a circuit is closed from ground G through wiper 54, relay 51,and wiper 53, to the battery B. A circuit is also closed from ground Gthrough wiper 54, wiper 42, and the cut-off winding 65 of line switch Fto the battery B. The wind ing operates to disconnect the line relay 67of the called line. The relay 51, upon energizing, breaks the circuit ofrelay 49, but the latter being slow acting will retain its armatureattracted for a short time atterits 'circuit is broken. A further resultof the energization of relay 51 is the completion of the line circuitrover heavy conductorsthrough wipers 41 and '43 to the line ofsubstation J. It should be noted that ringing ground. G through currentwill be immediately applied to the called line over a circuit thatextends from the non-grounded terminal of the generatorR through springs112 and 111 of relay 19, springs 113 and 11st of relay 50, springs 115and 117, wiper 41, line conductor 11S, condenser and ringer of stationJ, return con ductor 119, wiper 13, springs 120, springs 121 and 122,left hand whirling of relay 550, battery B to ground and thence togenerator ground G to other terminal of the generator When wiper 53passes to third position another circuit is closed from ground G throughinterrupter 61., group relay 60, and side switch wiper to the battery B.The relay 60 is energized intermittently due to the insulated andnoninsulated portions on the interrupter 61. The preliminary applicationof ringing current is controlled by the clay 4:9 and is thereforeabsolutely independent of the energizetion or deenergization of relay60. springs 109 and 110 are separated due to the energization of relay51 the circuit of relay 19 is broken; a short time after this occurs thelatter relay deenergizes and closes its springs 111 and 123, therebycompleting the generator circuit controlled by the interrupter relay 60so that said relay 60 will thereafter intermittently connect thegencrater R to the called line. When relay 60 is energized and afterrelay 4:9 is deenergized ringing current flows from the non-groundedterminal of generator It through springs 12 1 and'125, springs 123and111 thence over the circuit as previously traced over the called line.When relay G9 is deenergized, the booster battery B is connected overthe same circuit through springs 126 and 125. The booster battery B willthen be connected in a series circuit with the left-hand winding ofrelay 50 and the battery B. The function of the battery B, as beforeexplained, is to provide an increased flow of current whereby telephonelines of high resistance will have no diiiiculty in operating relay 50to cut oil the ringing. The relay 50 will not operatively energize whengenerator current flows through it in series with a condenser; however,as soon a direct metallic circuit is established the said relay 50 willattract and fully operate its armature. Upon the removal of the receiverat station J, current will. flow either from generator R or boosterbattery B depending upon position of spring 125, through springs 123 and111, springs 113 and 114s, springs 115.and 117, wiper 41, line conductor118, switch hook springs 127. impulse springs 128, receiver 129,transmitter 130, return line conductor 119, wiper 43, springs 1.29springs 121 and 122, left hand winding of relay 59 to the battery B andground either at ground G or grounded terminal of battery B. The relay50, upon energizing, forms a locking When circuit from ground G throughsprings 59, springs 131 and the right hand winding of said relay 50 tothe battery B. A further result of the euergization of relay 50 is theseparation oif springs 11% and 113 and springs 121 and 122 and theclosure of springs 11 and 132, as well as springs 121 and 133, whereby acircuit for the back bridge relay 56 is completed from ground G throughsprings 59, springs 131 of relay 59, right-hand winding of said relay56, springs 13% and 121 to and through substation J as before traced tosprings 114: and 132, thence through the leitdiand winding of relay 56to the battery B. The backbridge relay 56 is the medium through which ithe called subscriber is supplied with current for talking purposes. Thesaid rela 56 upon energizing, reverses the direction 0 current flow onthe calling line and by shitting spring 13a out of engagement withspring 185 and into engagement with spring 136 opens a contact in thecircuit of release a magnet 57 and prepares a circuit for relay 4:8 Theconnections are new in talking condition and the subscribers mayconverse; talking current traveling over the heavy conductors.

Upon the completion of the conversation the connection will be releasedas follows, assumin that the called subscriber hangs up his receiveriirst and thereby deenergizes back-bridge relay 56. l Vhen the callingsubscriber hangs up his receiver and thereby breaks the contact ofsprings 70, the circuit of line relay d6 of connector H is broken,which, upon deenergizing, breaks the circuit of relay e7, which in turn,upon debnergizing, removes the holding ground G from the releaseconductor 100, and in addition closes a circuit from ground G throughsprings 98 and 13'}, springs '58, springs 13 i and 135 and the releasemagnet 57 t0 the battery B. The release magnet, upon ener rizing,operates to restore the switch. sh aft side switch wipers to theirnormal position... its own circuit being opened when said shaft reachesits normal position and separates springs 58 and 59.

[is soon as private wiper -12 disengages bank contact 138, caused by therelease of the connector, the circuit of winding 65 of-the switch F isbroken to permit the line relay 6'? to be placed within control of thesubstation J. "When the holding ground is removed from the releaseconductor 100, the circuit of relay 37 and holding winding is broken,The relay 37, upon dee'ner- ;izing, closes a circuit from ground Grhrough springs C 7 and 8%, springs 85, prings 86 and 139, springs 39 andthe remagnet 38 to the battery B. The :se magnet, upon energizing,restores the switch shaft and wipers to normal position. The shaft uponreaching its normal position opens the circuit of said release magnet atsprings 39. The deenergizatlon of winding 15 of the line switch Creleases the plunger arm 13 and cut-off arm 12, thus permitting thewithdrawal of the plunger from its bank contacts and the restoration ofthe line relay 11 across the conductors of the calling line. If,however, the calling subscriber restores his receiver to its switchhookbefore the called subscriber has done so, then the connector switch willnot be released, but the selector E and line switch C will be returnedto their normal position. This condition is brought about as follows:The calling subscriber upon hanging up his receiver, opens the circuitof the line relay 46 which opens the circuit of relay 47, the latterremoving ground (i from'the con ductor 100v thereby permitting switchesE and C to be releasedin the manner hereinbefore described. Relay 56being now energized, a circuit will be closed from ground i throughsprings 98 and 137, springs 58, springs 134 and 136, springs 140 and106, private control relay 48, conductor 141,

springs 142 and 110 of relay 51 and the lower winding of relay 55 to thebattery B.

Relay 55 does not operatively energize at this time, its lower windingbeing for the purpose of reducing the current flow through relay 48.Relay 48 energizes over this circuit and closes a circuit from ground Gthrough springs 107 and 108 and the private magnet 52 to the battery B.The private magnet upon energizing, closes a circuit from ground Gthrough springs 143 over release conductor 100 to selector private bankcontact 144 and multiples thereof. This ground potential protects theconnector from seizure as longas it is held in this position. When thecalled subscriber hangs up his receiver thereby separating switch hooksprings 127, the circuit of back bridge relay 56 is broken, thereupondeenergizing said relay to release the switch in the manner previouslydescribed.

If the called substation is busy there will be a guarding groundpotential on private bank contact 138 and its multiples, there-- forewhen connection isattempted and the private wiper 42 engages saidcontact, a circuit is closed from ground thereon over said wiper 42,side switch wiper 54 (in second position) through springs 145 and 146,

upper winding of relay 55, spring 147 and 108' and the private magnet 52to the battery B. The relay 55 energizes over this circuit, to open therotary magnet circuit at springs 116, to form a locking circuit foritself by forcing spring 148 into contact with spring 146 and separatingspring 145 therefrom. This circuit extends from ground G through springs59, springs 148 and 146, thence over the circuit previously traced. Therelay 55 is held energized over this circuit and through the contact ofits springs 149 supplies a busy tone from the busy machine I to thecalling substation. The circuit for said tone extends from the batterylead through transformer winding 63, springs 149, over heavy conductorsto and through substation A, back overheavy conductors and the upperwinding of the line relay 46 to the battery lead. The sub scriberreceives the tone in his receiver and upon recognizing the fact that theline is busy, restores his receiver to'release the automatic switches ina similar manner to that herein described;

t is thus seen that this invention contemplates a very efficient form ofconnector switch which applies ringing current to signal the calledstation as soon as connection is completed therewith. in this mannor thesignal of the called station is in stantly operated. It is also seenthat called lines are assisted in cutting off the ringing through themedium of the booster battery.

lVhile the illustration and description of this invention has beenconfined to an automatic switch of a particular type it is to beunderstood that I do not wish to be so limited as the principles hereinset forth may be applied to various other circuit arrangements or typesof apparatus without departing from the spirit and scope of thisinvention.

What I claim as my invention is:

1. In a. telephone system, a calling line, a called line, a plurality ofprogressively movable switches, any one, of which will serve the purposeof the calling line for establishing a connection to said called line, asignal for the called line, a source of current for operating saidsignal, a circuit in dividual to one of said switches, a circuit commonto said switches, means for con necting said source over said individualcircuit to operates-aid signal and for then connecting said source oversaid common circuit to said signal to operate the same, and means forinterrupting said common circuit to intermittently operate. said signal.

2.1n a telephone system, a callinglin'e, a called line, a plurality ofsets of progressively movable switches, any set of which will serve thepurpose of the calling line for extending a connection to the calledline, a signal for the called line, asource of current for operatingsaid signal, acircuit common to said switches for connecting the saidsource with said signal when said connection is established, means forinterrupting said circuit to intermittently operate said signal, andmeans including a circuit individual to one of said switches andindependent of said interrupting means for connecting said source withsaid signal to operate the same. 7

3. In a telephone system, a calling line,

a called line, a plurality of progressively movable switches, meanswhereby the calling line finds one of said switches to extend aconnection to said called line, a signal for said called line, a sourceof current for operating said signal, a circuit individual to one ofsaid switches, a circuit common to said plurality of switches, means forconnecting said source and said signal over said individual circuit tooperate said signal and for then connecting saie source and said signalover said common circuit to operate said signal over said commoncircuit.

4. In a telephone system, a calling line, a called line, a plurality ofprogressively movable switches, means whereby the calling line finds oneof said switchesto extend a connection to said called line, a signal forsaid called line, a source of current for operating said signal, acircuit individual to one of said switches, a circuit common to saidplurality of switches, means for connecting said source and said signalover said individual circuit to operate said signal and for thenconnecting said source and said signal over said common circuit tooperate said signal over said common circuit, and means forintermittently interrupting said common circuit to intermittentlyoperate said signal.

5. In a telephone system, a line, a signal for said line, means foroperating said signal, a plurality of circuits for connecting said meansand said signal, means for shitting the line from one of said circuitsto another to operate said signal over either of said circuits, vmeansfor interrupting one of said circuits to intermittently operate saidsignal, a battery for operating said second means, another battery, saidlast means also for including said batteries in series with said line toenable said line to disconnect said first means.

6. In a telephone system, a line, a signal for said line, means foroperating said signal, a pair of circuits for connecting said means andsaid signal, means for controlling the operation of said signal firstover one of said circuits and then the other, means for interrupting oneof said circuits to intermittently operate said signal, a battery foroperating said second means, another battery, said last means also forincluding said batteries in series with said line to enable said line todisconnect said first means.

7. In a telephone system, a line, a signal for said line, a pair ofcircuits, means for operating said signal, said means associated withsaid circuits, means for connecting said operating-means and said signalover one of said circuits to operate said signal thereover, and forconnecting said means and said signal over the other of said circuits tooperate said signal over said other circuit, and means forinten'uptingsaid other circuit to intermittently operate said signal, abattery for operating said second means, an other battery, said lastmeans also for including said batteries in series with said line toenable said line to disconnect said first meansL i 8. In a telephonesystem, a line, a signal for said line, a source of current foroperating said signal, a circuit comprising two branches for connectingsaid source over said line to said signal, means for closing one of saidbranches to operate said signal and for opening said last branch andclosingthe other of said branches to control the operation of saidsignal, means for interruptingsaid other branch to intermittentlyoperate said signal, a battery for operating said first means, anotherbattery, said last means also for including said batteries in a circuitwith said line to enable said line to disconnect said source of current;

9. In a telephone system, a calling line, a called line, a signal forthe called line, a source of current for operating said signal,progressively movable switching, mechanism for establishing a connectionfrom said calling line to said called line, a pair of circuits, meansfor connecting said source. and said signal over one of said circuits tooperate vals, a battery for operating said first means, another battery,said last means also for including said batteriesv in a circuit withsaid line to enable said line to disconnect said source of current.

10. In a telephone system, a calling and a called line, progresslvelymovable automatic switches for establishing a conne tion between saidlines, a signal for the called line, a source of current for operatingsaid signal, a circuit comprising two branches for connecting saidsource to said signal after said connection is established, means forclosing one otsaid branches to operate said signal and'for thereafteropening said last mentioned branch and closing the other branch tooperate said signal, and means for interrupting said other branch tointermittently operate said signal, a battery for operating said firstmeans, another battery, said last means also'for including saidbatteries in a circuit with said line to enable said line to disconnectsaid source of current.

11. In a telephone system, a calling line,

a called'line, a plurality of progressivelysignal for the called line, asource of cur;

rent for operating said signal, a circuit individual to one of saidswitches, a circuit ing said source over said common circuit to saidsignal to operate the same, and means for interrupting said commoncircuit to intermittently operate said signal, a battery for operatingsaid first means, another battery, said last means also for includingsaid batteries in a circuit with said line to enable said line todisconnect said source of current. a

12. In a telephone system, a calling line a called line, a plurality ofprogressively movable switches, means whereby the call ing line findsone of said switches to extend a'connection to said called line, asignal for said called line, a source of current for operating saidsignal, a circuit individual to one of said switches, a circuit commonto said plurality of switches, means for connecting said source and saidsignal over said individual circuit to operate said signal and forthenconnecting said source and said signal over said common circuit tooperate said signal over said common circuit, and means forintermittently interrupting said common circuit to intermittentlyoperate said signal, a battery for operating said second means, anotherbattery, said last means also for including said batteries in a circuitwith said line to enable said line to disconnect said source of current.a

13. In a telephone system, a first line, a callingline, a signal forsaid first line, a source of current for operating said signal, abattery for operating purposes, a relay for disconnecting said source,means for connecting said calling line and said first line and forincluding said relay and battery in circuit during signaling wherebywhen the first line answers if the said first line is short the relaywill energize to cut ofl said source of current but it the line is longthe relay "fails to operate, another battery, and means for thereafterincluding said batteries in the circuit of said relay to enable saidfirst line to operate said relay todisconnect 5 said source of currentif the said first line is long.

14. In a telephonesystem, a calling'line, a called line, a plurality ofprogressively movable switches, any one of which will serve the purposeof the calling line for establishing a connection to said called line, asignal for the called line, a source of current for operating saidsignal, a circuit individualto one of said switches, a circuit common tosaid switches, a slow magnet for connecting sald source over saidindlvldual circuit to operate said signal and for then connecting saidsource over said common circuit to said signal to operate the same, anda magnet for interrupting said'co'rnmon circuit to intermittentlyoperate said signal.

15. In a telephone system, a calling line, a called line, a plurality ofsets of progressively movable switches, any set of which will serve thepurpose of the calling line for extending a connection to the calledline, a signal for the called line, a source of current for operatingsaid signal, a circuit common to said switches for connecting the saidsource with said signal when said connection is established, a magnetfor interrupting said circuit to intermittently operate said signal, anda slow magnet including a circuit individual to one of said switches andindependent of said interrupting magnet for connecting said source withsaid signal to operate the same.

16. In a telephone system, a calling line, a called line, a plurality'of'progressively movable switches, means whereby the calling linefinds'one. of said switches to extend a connection to said called line,a signal for said called line, a source of current for operating saidsignal, a circuit individual to one of said switches, a circuit commonvto 'saidplurality of switches, a magnet for connecting said source andsaid signal over said individual circuit to operate said signal and forthen connecting said source and said signal over said common circuit tooperate said signal over said common circuit.

- '17. In a telephone system, a calling line, a called line, a pluralityof progressively movable switches, means whereby the calling line findsone of said switches to extend a connection to said called line, asignal "for said called line, a source of current for operating saidsignal, a circuit individual to one of said switches, a circuit commonto said plurality of switches, a slow magnet for connecting said sourceand said signal a over said individual circuit to operate said signalfor then connecting said source and said signal'over said common circuitto operate said signal over said common circuit.

18. In a telephone system, a calling line, a called line, a plurality ofprogressively movable switches, meanswhereby the calling line finds oneof said switches to extend a connection to said called line, a signalfor said called line, a source of current for operating said signal, acircuit individual to one of said switches, a circuit common to saidplurality of switches, a relay for connecting said source and saidsignal over said indi,-

vidual circuit to operate aid signal and for 7 ing said source ofcurrent and said signal, a slow magnet for controlling the operation ofsaid signal over one of said circuits and then the other, a magnet forinterrupting one of said circuits to intermittently operate said signal,a battery for operating said second magnet, another battery, said secondmagnet also for including said batteries in series with said line toenable said line to discon nect 'said source of current.

20. In a telephone system, a line, a signal for said line, a source ofcurrent for operating said signal, a circuit comprising two branches forconnecting said source over said line to said signal, a slow relay forclosing one of said branches to operate said signal and for opening saidlast branch and closing the other of said branches to control theoperation of said signal, a relay for interrupting said other branch tointermittently operate said signal, a battery for operating said slowrelay, another battery, said second relay also for including saidbatteries in a circuit with said line to enable said line to disconnectsaid source of current.

21. In a telephone system, a calling line, a called line, a signal forthe called line, a source of current for operating said signal,progressively movable switching mechanism for establishing a connectionfrom said calling line to said called line, a pair of circuits, a magnetfor connecting said source and said signal over one of said circuits tooperate said signal when connection is completed to said called line andfor then connecting said source and said signal over the other of saidcircuits to operate said signal over the other circuit, and anothermagnet for interrupting said other circuit to operate said signal atintervals, a battery for operating said magnet, another battery, saidother magnet also for including said batteries in a circuit with saidline to enable said line to disconnect said source of current.

22. In a telephone system, a calling line, a called line, a signal forthe called line, a source of current for operating said signal,progressively movable switching mechanism for establishing a connectionfrom said calling line to said called line, a pair of circuits, a slowrelay for connecting said source and said signal over one of saidcircuits to operate said signal when connection is completed to saidcalled line and for then connecting said source and said signal over theother of said circuits to operate said signal over the other circuit,and a relay for interrupting said other circuit to operate said signalat intervals, a battery for operating said first slow relay, anotherbattery, said second relay for including said batteries in a circuitwith said line to enable said line to disconnect said source of current.

Signed by me at Chicago, Cook county, Illinois, this 21 day of April,1916.

TALBOT G. MARTIN.

